CN111065479B

CN111065479B - Drilling blade

Info

Publication number: CN111065479B
Application number: CN201880057275.5A
Authority: CN
Inventors: 哈坎·卡尔贝里; 弗里茨·阿卢姆·亚赫
Original assignee: Sandvik Intellectual Property AB
Current assignee: Sandvik Intellectual Property AB
Priority date: 2017-09-06
Filing date: 2018-08-24
Publication date: 2022-07-08
Anticipated expiration: 2038-08-24
Also published as: RU2020112297A3; KR20200050958A; US11103935B2; EP3453477A1; JP7289829B2; JP2020532439A; KR102598371B1; RU2771284C2; CN111065479A; RU2020112297A; US20210060664A1; WO2019048265A1

Abstract

A metal cutting drill insert (15) for a drilling tool has a chip breaker (28) provided on a rake surface (25). The chip breaker is also configured with a chamfer (29) in the leading cutting edge region (26) to increase cutting resistance and promote chip breaking.

Description

Drilling blade

Technical Field

The present invention relates to a metal cutting drilling insert for a drilling tool having a chip breaker disposed on a rake surface of the insert, the chip breaker being configured to promote chip breaking and to produce small chip fragments during drilling.

Background

Rotatable drilling tools may be used for specific applications of workpiece machining in addition to general cutting tools and milling tools. Conventionally, indexable drilling tools comprise at least two separate inserts, wherein a central insert is mounted in the axial center of the tool and the peripheral inserts represent the radially outermost part of the cutting area. Thus, during rotation of the tool, the central insert, which is axially forward relative to the peripheral insert, forms an annular groove in the workpiece. As the tool continues to rotate and axially advance, the peripheral cutting insert, which is positioned to overlap the center insert, cuts into the workpiece through the radially overlapping swept areas of the center and peripheral inserts to radially extend the initial groove. Thus, the drilled hole is formed by a coordinated cutting action. Typically, the workpiece chips produced by the insert are directed rearwardly by chip flutes, which extend axially from the forward cutting region of the tool. An exemplary double-bladed drilling tool is described in EP 1902799.

However, a problem with existing drilling tools having one or more cutting inserts is that due to insufficient discharge of chips from the drilled hole, there is a tendency for workpiece chip formation to reduce drilling efficiency. Most commonly the chips form tangled balls or helical columns which build up on the cutting machine (usually CNC or multi-operator) and hinder uninterrupted and continuous cutting.

In addition, the high demand application of drill inserts generates high operating temperatures and stresses on the inserts, which in turn accelerates insert wear and fatigue, particularly in the region of the cutting edge. This greatly shortens the blade operating life. Accordingly, there is a need for an insert and a drilling tool with an attached insert that addresses the above-mentioned problems.

Disclosure of Invention

It is an object of the present invention to provide an insert for a drilling tool, which is configured to produce shorter chip fragment lengths and in particular to avoid the production of chips formed in the form of tightly curled balls or long helical bands. It is therefore a general object to provide a drilling insert for cutting metal which is capable of very efficient drilling and producing a bore hole.

A particular object is to provide an insert for a drilling tool configured to promote fracture and breakage of a workpiece chip as the chip is formed at a cutting region of the insert. It is therefore an object to facilitate the transport of chip fragments axially rearwardly from the formed drill hole to prevent clogging or plugging of the hole which would otherwise impede the continued axial advancement of the drilling tool. Another specific object is to provide an insert that facilitates the breaking of chips without weakening the insert due to wear and fatigue encountered during cutting. Another object of the invention is to provide a blade which does not impair the drilling stability, in particular does not disrupt the smooth rotational movement required for the drilling tool.

These objects are achieved by providing a cutting insert that is firstly configured to facilitate the formation of chips that are more easily broken and fractured, and secondly configured to encourage the fracture of the formed chips either immediately or shortly after they are produced from the workpiece. This is advantageous in order to minimize the chip size and thus facilitate the chip evacuation from the formed drill hole. These objects are particularly achieved by a blade having a raised or recessed chip breaker (alternatively, also referred to herein as a chip breaker) positioned at the rake surface of the blade immediately behind the cutting edge. The chip breaker is accordingly configured to provide an obstruction that is positioned within the path of the generated chips to induce mechanical stress to the chips and encourage their breakage. These objects are further achieved by providing a chamfer on the leading portion of the chip breaker at the region of the cutting edge of the insert. A chamfer can be considered to mean the intersection of the adjoining rake and clearance surfaces, and is defined relative to the remainder of the cutting edge (at one or both sides of the chip breaker), which can be considered to be unbevelled, and has a different shape profile. That is, and preferably, the above-described remaining portion of the cutting edge (defined by the intersection of the rake face and the clearance face) can be considered sharp, angled or acute with respect to the chamfered (alternatively referred to as chamfered) portion of the cutting edge in the region of the chip breaker. The chamfer includes an intersecting surface (the transition between the rake surface and the clearance surface) that may be substantially planar and aligned transverse to the rake surface and the clearance surface. Alternatively, the intersecting surfaces may be curved, including one or more radii of curvature in a plane perpendicular to the length of the cutting edge, as defined in a transverse direction across the insert between the first and second lateral sides.

The chamfer (with intersecting surfaces) is beneficial in increasing the cutting resistance of the blade, particularly in the region of the chip breaker. Thus, the cutting portion of the tool includes a greater cutting resistance in the region of the chip breaker relative to the location on one or either side of the chip breaker at the remainder of the cutting edge. Thus, when formed, the chips are heated to a greater extent in the region of the chip breaker and become correspondingly more brittle and therefore more prone to fracture and breakage. Positioning and positioning the raised or recessed chip breaker (disposed at the rake face immediately behind the leading cutting edge in the direction of rotation of the tool) in the path of the growing chip provides an obstacle facilitating fracture and breakage of at least the above-mentioned brittle portion of the chip.

According to a first aspect of the present invention, there is provided a metal cutting drilling insert for a drilling tool, comprising: at least one cutting edge formed at the intersection of adjoining rake and clearance surfaces, the cutting edge having a length that is radially aligned at the tool; a chip breaker formed at the rake face as an elevated protrusion or recess and extending from the cutting edge; the method is characterized in that: a chamfer at the intersection of the rake surface and the clearance surface and positioned at the chip breaker, the chamfer being defined relative to the profile of the cutting edge at one or either side of the chip breaker.

The insert of the present invention has a chamfer extending only partially along the cutting edge, which further facilitates chip breaking without compromising the stability of the cutting tool, which would otherwise be reduced by the presence of the high resistance cutting edge region. Thus, the insert of the present invention provides a stable cutting action in that the chamfer extends only along a portion of the total length of the cutting edge as defined between the first and second lateral sides of the insert (e.g., less than 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the total length of the cutting edge), wherein the insert is positionable on a drilling tool such that the first lateral side is disposed radially inward and the second lateral side is disposed at the radially outermost portion of the tool to define the diameter of the axially forwardmost cutting region.

Preferably, the drilling inserts are configured to cooperate with second inserts, the inserts being mountable on the tool at different radial positions such that during rotation of the tool the inserts radially overlap to define an annular intersection region; wherein the chip breaker is positioned relative to the cutting edge in the intersection region. In particular, the inventors have recognized that by locating the chip breaker (and thus the chamfer) at the region of the intersection region, the effectiveness of the chamfer and chip breaker in inducing and promoting chip breaking is maximized. That is, at the region of radial overlap of the peripheral and central inserts, it has been observed that this portion of the formed chip is weakest. Thus, the length (in the longitudinal direction of the cutting edge) of the chamfer and chip breaker can be minimized in order to keep any instability of the tool during use that is increased by the presence of the chamfer to a minimum while promoting chip breaking. In addition, by keeping the length of the chamfer to a minimum (sufficient to achieve chip breaking), the life and working life of the insert is maximized.

As indicated, the cutting portion (represented by the cutting edge) of the insert includes a different shape profile at the chip breaker relative to the remainder of the cutting edge on one, either or both sides of the chip breaker. That is, the above-mentioned remaining portion of the cutting edge may be formed as a relatively "sharp" intersection of the rake face and the clearance face, while the cutting region of the chip breaker is chamfered. Thus, the cutting portion of the insert at the chip breaker is distinguished from the above-mentioned remaining portion of the cutting edge by the shape profile produced by the chamfer. Optionally, the above-mentioned remaining part of the cutting edge may have a chamfer, a bevel or be rounded according to one or two radii. However, for any such configuration, the chamfer (formed by a generally planar surface or a curved or rounded surface) will always have a different shape profile than the above-described remainder of the cutting edge.

Preferably, the chamfer at the chip breaker defines a generally planar intersecting surface. Preferably, the intersecting surface is aligned transverse to the adjoining rake and clearance surfaces, and the cutting edge at one or either side of the chip breaker is free of intersecting surfaces, and has i) a line shape and/or ii) a width extending between the rake surface and the clearance surface, the line shape and/or width corresponding to the line shape and/or width of the intersecting surfaces at the chip breaker.

Preferably, the length of the chip breaker in the longitudinal direction along the rake surface is less than the remaining length of the cutting edge between the lateral sides of the insert at one or both sides of the chip breaker. Such an arrangement minimizes any instability of the drilling tool that is increased by the presence of the chamfer. Preferably, the length of the chip breaker is from 5 to 60%, 10 to 50%, 20 to 40%, 30 to 40% or 30 to 35% of the total length of the cutting edge, including the chamfer and the cutting edge at one or both sides of the chip breaker between the lateral sides of the insert.

Preferably, the insert comprises a single chip breaker at the rake face. The chip breaker is defined in the longitudinal direction of the rake face (corresponding to the transverse direction across the insert) by respective first and second transition regions formed as upwardly or downwardly inclined surfaces. Such transition region surfaces at the rake face are inclined upwardly or downwardly with respect to a plane aligned perpendicular to the longitudinal axis of the tool, their orientation depending on whether the chip breaker is an elevated protrusion (formed as a rib, step, hump or bump) or a recess (formed as a groove, channel or cavity) at the rake face. Optionally, the chip breaker extends across the entire width of the rake face (corresponding to the longitudinal direction of the insert). Such an arrangement is advantageous in maximizing the strength of the chip breaker and minimizing stress concentrations during cutting. The presence of a single chip breaker is advantageous in minimizing any cutting instability of the drilling tool due to the presence of the chip breaker and chamfer while achieving adequate chip breaking. Alternatively, the chip breaker may extend partially across the rake surface (in a direction perpendicular to the length of the cutting edge).

Preferably, the chamfer at the chip breaker comprises intersecting surfaces and the intersecting surfaces are aligned in a plane perpendicular to the length of the cutting edge in the range of 20 ° to 70 °, 25 ° to 65 °, 30 ° to 60 °, 35 ° to 55 °, or 40 ° to 50 ° relative to the clearance face. Such an arrangement is advantageous in providing sufficient cutting resistance in the region of the chip breaker to thereby increase the brittleness of the formed chips.

Preferably, the blades are peripheral blades intended to cooperate with a central blade of the drilling tool, the peripheral and central blades being defined in position in a radial direction with respect to each other and with respect to a longitudinal axis of the drilling tool. Preferably, the central insert and the peripheral insert comprise through holes to receive mounting screws for attachment to the drilling tool. Preferably, the central insert and the peripheral insert may be indexable, i.e.: including first and second cutting edges (defined by respective rake and clearance surfaces) disposed at opposite longitudinal ends of each respective insert. According to further embodiments, the peripheral insert may comprise one, two, three, four or more cutting edges at one side and/or one, two, three, four or more cutting edges at the opposite side.

Optionally, the insert (including peripheral and central inserts) comprises a generally rectangular cuboid shape in which the cutting edge extends laterally across the insert at one, two, three, four or more edges of the insert, wherein the insert may be indexable. Alternatively, the cutting area of the insert may be enlarged such that the insert width is greater at the cutting area relative to a central area of the insert (corresponding to an intermediate length area of the insert in the direction between the end clearance faces) in a transverse direction across the insert.

Preferably, the chip breaker is positioned on the insert in the longitudinal direction of the cutting edge closer to the first lateral side of the insert than to the second lateral side of the insert. This configuration positions the chip breaker at the region of the intersection (the radially overlapping region of the central and peripheral blades) to maximize chip breaking efficiency. Such an arrangement is advantageous for providing a universal peripheral blade adapted to be mounted on drilling tools of different diameters, wherein the chip breaker is positioned at the intersection area defined by the rotational paths of the central blade and the peripheral blade.

Preferably, the chip breaker is positioned in the longitudinal direction of the cutting edge only in the first half of the insert closer to the first lateral side. Alternatively, the chip breaker may extend from a first radially inner half of the cutting edge to a second radially outer half of the cutting edge. Preferably, the majority of the chip breaker is located within the first half of the insert, which is intended to be mounted closest to the axial center of the tool, which corresponds to the area intersecting (radially overlapping) the central insert.

Optionally, a portion of the cutting edge is curved or angled in a longitudinal direction of the cutting edge such that a second end of the cutting edge closest to the second lateral side of the insert is raised relative to a first end of the cutting edge closest to the first lateral side of the insert. Preferably, a portion of the cutting edge closest to the second lateral side surface is concave to curve upwardly towards the second end of the cutting edge when the insert is viewed end-to-end from the clearance surface. Such an arrangement is advantageous to facilitate and favour the generation of tightly curled chips which accordingly occupy a reduced volume within the bore and are therefore more easily evacuated during drilling. Thus, the life of the insert and the drilling tool is extended. When mounted on a drilling tool, the cutting edge is preferably curved and concave at a radially outer region of the insert, such that a radially outer end of the cutting edge projects forward (in the direction of rotation of the drilling tool) relative to a central region and a radially inner region of the cutting edge. According to a preferred embodiment, the radially outer end of the cutting edge protrudes at an elevated or forward position with respect to the mid-length region of the cutting edge and the radially innermost end of the cutting edge. Thus, the insert may be considered "thicker" at the radially outer end to have a "wedge-shaped" profile at the radially outer region. This raised outer region of the cutting edge cuts into the workpiece to a greater extent and before the radially inner region of the insert to provide lift and curling of the chip during drilling.

According to a second aspect of the present invention, there is provided a metal cutting drilling tool comprising: an elongated drilling body having an axially forward drilling shaft and an axially rearward mounting shank; and a drill insert as claimed herein mountable at an axially forward end of the shaft. The cutting insert may be mounted such that the cutting edges are aligned in a radial direction or in a substantially radial direction, i.e.: the cutting edges are aligned in a direction from a central region toward a periphery of the drill body. For example, the extension of the cutting edge may intersect the longitudinal axis of the drilling body or a point near the longitudinal axis of the drilling body.

Preferably, the insert is mounted in a radially peripheral region of the drilling tool to form a peripheral insert. Preferably, the tool comprises a second cutting insert mounted at or towards a radially central region of the drilling tool to form a central insert with respect to the peripheral inserts. Preferably, the cutter comprises a single peripheral insert and a single central insert mounted at the axially forward end of the shaft.

Preferably, the peripheral and central blades are mounted on the drilling tool such that during rotation of the drilling tool the blades radially overlap to define an annular intersection region; wherein the chip breaker is positioned in the intersection region relative to the cutting edge.

Preferably, a substantial portion of the chip breaker is positioned within the intersection in the radial direction. Alternatively, the chip breaker may extend in the longitudinal direction of the cutting edge (corresponding to the transverse direction across the insert) beyond the intersection region that includes a small or large portion of the chip breaker. Thus, the insert of the present invention may be adapted to provide and promote chip breaking at a desired radial position of the formed chips relative to the axial center of the drilling tool.

Preferably, the shaft includes flutes extending axially rearwardly from the axially forward end toward the mounting shank. Preferably, the central and peripheral inserts are positioned at an axially forward end of each respective chip flute such that the respective cutting edges of the inserts are configured to produce chip chips that are propelled directly into the chip flutes for rearward discharge from the drill hole.

Drawings

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 is a perspective view of an elongated drilling tool having a pair of cutting inserts mounted thereon, the cutting inserts including a center insert and a peripheral insert, according to an embodiment of the present invention;

FIG. 2 is another perspective view of the drilling tool of FIG. 1;

FIG. 3 is an axial end view of the cutting end region of the drilling tool of FIG. 2;

FIG. 4 is a perspective view of a peripheral cutting insert of the drilling tool of FIG. 3;

FIG. 5 is another perspective view of the peripheral cutting insert of FIG. 4;

FIG. 6 is a plan view of the peripheral cutting insert of FIG. 5;

FIG. 7 is an end view of the peripheral cutting insert of FIG. 6 as viewed from the cutting region;

FIG. 8 is a cross-sectional view through VIII-VIII of the peripheral cutting insert of FIG. 6;

FIG. 9 is a perspective view of a peripheral cutting insert of the drilling tool of FIG. 3 according to another embodiment;

fig. 10 is an end view of the peripheral cutting insert of fig. 9 according to another embodiment;

FIG. 11 is a perspective view of a peripheral cutting insert having a cutting edge profile configured to promote chip curl, according to another embodiment;

fig. 12 is an end view of the peripheral cutting insert of fig. 11 as viewed from the cutting edge region.

Detailed Description

Referring to fig. 1 and 2, an indexable insert drilling tool particularly suitable for cutting metal includes a drilling body 10, the drilling body 10 having an axially rearward shank 12 for mounting the drilling body 10 in a drill press and an axially forward shaft 11, the axially forward shaft 11 having an axially forward cutting end 13. The shaft 11 includes a pair of diametrically opposed flutes 17, the flutes 17 extending axially and helically about the central longitudinal axis 14 of the drill body 10 from the axially forward cutting end 13 toward the rear end of the shaft 11. Referring to fig. 3, a pair of bores 20 extend axially through the drill body 10 to provide for the delivery of flushing fluid. A pair of wear resistant cutting inserts are mounted at the axial forward cutting end 13 of the shaft, which axial forward cutting end 13 of the shaft comprises in particular a central insert 16 and a peripheral insert 15. Each

insert

15, 16 includes a hole 30 (holes of the peripheral insert 16 are shown in fig. 4-6) to receive a mounting screw (not shown) for attachment to the shaft 11 of the drill. The central insert 16 comprises a leading cutting edge 21 and the peripheral insert 15 comprises a corresponding leading cutting edge 26.

Referring to fig. 1-3, the drilling body 10 is configured to be rotatable about the axis 14 in a direction R such that the cutting edges 21, 26 are configured to be cut into a workpiece material (not shown) by axial advancement of the drilling body 10 to produce a drill hole having a diameter corresponding to the diameter of the cutting tool as determined by the peripheral insert 15. With particular reference to fig. 3, an axial end view of the cutting tool may be separated by two perpendicular imaginary planes P1 and P2 that intersect at the axis 14. The peripheral cutting insert 15 is positioned entirely on one side of the P1 plane, while the majority of the central insert 16 is positioned on the opposite side of the P1 plane. The cutting edges 21, 26 of both

inserts

16, 15 are located at or near the plane P2. According to this particular embodiment, the central blade 16 is aligned transversely to the plane P2 such that the radially outer side of the central blade 16 is positioned behind the radially inner side in the direction of rotation R of the drilling tool.

Referring to fig. 4 and 5, the peripheral blade 15 comprises a generally rectangular cuboidal profile having a generally rectangular front support face 23 (and corresponding rear support face 34). The first lateral side 27a represents a radially inner region of the insert 15 (when mounted on the drilling body 10) in which the face 27a is located closest to the axis 14. The blade 15 is further defined by a radially outer second lateral face 27b, which radially outer second lateral face 27b is located at the radial periphery of the shaft 11, so as to face radially outwards. The cutting edge 26 extends transversely (width) across the insert 15 between the

lateral sides

27a and 27b, and the cutting edge 26 is generally radially aligned at the drilling body 10, as shown in fig. 2-3. A cutting edge 26 is defined at the intersection of the rake surface 25 and the clearance surface 24. The rake surface 25 represents a concave extension of the support surface 23 and comprises an at least partially curved concave profile in a cross-sectional plane VIII-VIII through the insert 15 of fig. 6, as will be seen with further reference to fig. 8. The clearance surface 24 is declined from a plane perpendicular to the axis 14 such that when the insert 15 is mounted on the drilling body 10, the cutting edge 26 represents an axially directed portion of the insert 15 to cut into the workpiece material as the drilling body 10 rotates in the direction R. According to this particular embodiment, the clearance surface 24 may be considered to be divided into two regions in a transverse direction across the insert 15 (corresponding to the radial direction of the elongate drilling body 10). In particular, the clearance surface 24 includes a first radially inner region 24a and a second radially outer region 24b, the first and second radially

inner regions

24a, 24b being dimensioned to represent approximately radially inner and outer halves of the insert 15 in a transverse direction (corresponding to a longitudinal direction of the cutting edge 26 between the radially inner and

outer ends

26a, 26 b). The first radially inner region 24a of the clearance surface is aligned transverse to the second radially outer region 24b such that the cutting edge 26 is angled along its length at an angle in the range of approximately 158 ° to 162 °. Referring to fig. 8, at a cross-section VIII-VIII through the insert 15, the angle β between the clearance surface 24 and the axially forward region of the rake surface 25 is in the range of 70 ° to 80 °. So that the clearance surface 24 extends at an acute angle relative to the support surface 23. The arrangement is such that the leading cutting edge 26 is at least partially defined by an undercut at the axially forward leading region of the insert 15.

According to this embodiment, the insert 15 comprises a chip breaker (otherwise known as a chip breaker) in the form of raised protrusions provided on the rake surface 25. A chamfer, generally indicated by reference numeral 29, is provided in the guiding region (in the longitudinal direction of the insert 15) of the chip breaker 28, wherein the chamfer 29 is positioned at the intersection of the rake surface 25 and the clearance surface 24. That is, the chamfer 29 includes a first edge 29a corresponding in position to the main cutting edge 26 and a raised second edge 29b (aligned parallel to the first edge 29a), the second edge 29b having a height difference with respect to the first edge 29a (and the main cutting edge 26), as shown with reference to fig. 7 and imaginary planes H1 and H2. Thus, the chamfer 29 comprises an intersection surface 18 defined between the

edges

29a, 29b, aligned transversely to the axial guides of the clearance surface 24 and at least the rake surface 25. Referring to fig. 8, the angle α between the clearance surface 24 and the intersecting surface 18 of the chamfer 29 is in the range of 25 ° to 65 ° or more preferably 40 ° to 50 °. The chamfer 29 and particularly the intersecting surface 18 transitions into the chip breaker major face 32 approximately aligned with the plane P2 of fig. 2. In the plane VIII-VIII of fig. 6, the profile of the shape of the chip breaker major face 32 corresponds to the general profile of the shape of the rake surface 25 on one or either side of the chip breaker 28. Referring to fig. 8, the angle β between the clearance surface 24 and the axially forward or leading portion of the chip breaker major face 32 is in the range of 70 ° to 85 °.

According to this embodiment, the chip breaker 28 extends completely (transversely across the rake surface 25) between the cutting edge 26 (chip breaker leading edge 29a) and the rear end 31 of the rake surface 25 located at the junction with the support surface 23. According to further embodiments, the chip breaker 28 can be provided only at the forward region of the rake surface 25 in a direction towards the cutting edge 26. Advantageously, the embodiment of fig. 1-8 provides a structurally robust construction to withstand the high temperatures and stresses during cutting, thereby minimizing the possibility of stress concentrations at the insert 15. In addition to the inclined chamfer 29 (generally located at the cutting edge 26), the chip breaker 28 also includes a corresponding pair of

chamfered side surfaces

33a, 33b that provide a transition between the rake surface 25 and the chip breaker major surface 32 in the elevation direction between H1 and H2. The angle of the side faces 33a, 33b relative to the imaginary plane H1 is approximately equal to the angle alpha between the intersecting surface 18 and the clearance surface 24. Such an arrangement provides a smooth transition across and across the chip breaker 28 from the rake face 25 to minimize stress concentrations and further facilitate chip breaking.

As will be noted from fig. 6 and 7, the chip breakers 28, formed as raised ridges or shelves at the rake surface 25, are positioned in the radially inner half of the insert 15 in the radial direction of the drilling body 10 with respect to the axis 14. That is, the chip breaker 28 is positioned only within the radially inner zone Z1 relative to the radially outer zone Z2, wherein Z1 and Z2 are approximately equal in the radial direction of the drilling body 10 corresponding to the transverse direction across the insert 15. In particular, the length B of the chip breaker 28 is in the range of 20% to 45%, preferably 28% to 38%, of the total axial length L of the cutting edge 26 (including the chip breaker cutting edge 29a) located between the radially inner end 26a and the radially outer end 26B of the cutting edge.

Referring again to fig. 1-3, the central blade 16 is mounted axially forward of the peripheral blade 15 such that a workpiece (not shown) is first entered by the central blade to create an initial annular groove about the axis 14. By continuing rotation and axial advancement, the leading cutting edge 26 (and chamfer 29) of the insert 15 engages into the workpiece, forming an effective extension of the cutting edge 21 of the center insert 16. In particular, in the direction of rotation R, the central insert 16 and the peripheral insert 15 are radially positioned so that their

respective cutting edges

21, 26 and 29a overlap in an intersection zone corresponding to the inner zone Z1 of the peripheral insert 15. It is in this zone Z1 that the cutting of the workpiece is effected by the cooperation of the radially overlapping cutting edges of the two

inserts

16, 15. In accordance with this embodiment, the chip breaker 28 and chamfer 29 are positioned only in the intersection Z1 of the center blade 16 and the peripheral blade 15, relative to the overlapping rotational paths of the

blades

16, 15 about the axis 14. It has been found that a portion of the chip resulting from cutting in the intersection zone Z1 is more prone to chipping and that this intersection zone is at the region where the chamfer 29 is located to increase the cutting resistance and thus enhance the brittleness of the chip to facilitate chip breaking. It will be appreciated that both zones Z1 and Z2 are generally annular swept areas extending about the axis 14, and that the radial position of zone Z2 effectively defines the diameter of the borehole.

It is important that the cutting edge 26 is not beveled, but is formed as a relatively sharp intersection between the clearance surface 24 and the rake surface 25, both radially inward and radially outward of the chip breaker 28. That is, the chamfer 29 extends over a small portion of the transverse direction of the insert 15 relative to the total length L of the cutting edge 26, wherein the total length L of the cutting edge 26 includes the chamfer edge 29a and the cutting edge 26 at one or both sides of the chip breaker 28. Such an arrangement is advantageous to maximize the stability of the drilling body 10 during rotation while facilitating chip breaking. In particular, the chamfer 29 is configured to increase the cutting resistance of the insert when the drilling body 10 is rotated in the direction R. Thus, due to the increased resistance, the formed chip is heated, which in turn increases the brittleness of the chip, making it easier to break up. Thus, the elevated profile of the chip breaker 28 extending from the cutting edge 26 (chip breaker cutting edge 29a) provides an obstruction to the chip as it is formed at the rake surface 25. The combination of increased brittleness and the raised profile of the chip breaker 28 serves to continuously break and break chips as the cutter body is rotated in direction R. Thus, the subject invention is configured to keep the length of the formed chip to a minimum, and in particular to avoid the production of long helical chips or tightly curled chip balls, which would otherwise reduce drilling efficiency. The insert configuration of the present invention thus facilitates the evacuation of chips from the formed hole rearwardly through the chip flute 17.

With reference to fig. 9 and 10, another embodiment of the invention is described, in which the chip breaker 28 is formed as a recess or groove at the rake surface 25. That is, the major surface 32 of the chip breaker 28 is positioned at a lower height H1 relative to the height H2 of the rake surface 25 immediately behind the cutting edge 26. Similarly, the

chip breaker sides

33a, 33b extend transversely across the rake surface 25 to define the groove-shaped chip breaker 28, and the

lateral sides

33a, 33b are aligned at respective inclinations with respect to a plane perpendicular to the tool axis 14 that is coincident with the chamfer 29. The shape profile and orientation of the chamfer 29 according to this further embodiment of fig. 9 to 10 corresponds to the first embodiment of fig. 4 to 8, in which the inclined intersection surface 18 is oriented at an angle α relative to the clearance face 24. This same chip breaking mechanism applies to the second embodiment where the chamfer provides increased cutting resistance to change the physical and mechanical properties of the formed chip, where the chip is broken and fragmented by the height difference between H1 and H2 provided by the breaker main face 32 and the rake face 25. Again, the size and dimensions of the chip breaker 28 of the second embodiment are approximately equal to those of the first embodiment, having a length B in the radial direction of the drill body 10 and a width (in the longitudinal direction of the insert 15) extending completely across the entire width of the rake face 25 between the cutting edge 26 and the rake face rear end 31.

Fig. 11 and 12 illustrate another embodiment of the subject invention having a cutting edge 26 adapted to promote and facilitate chip curl. Most of the features and functions of the peripheral blade embodiment of fig. 2-10 are common to the other embodiment of fig. 11-12. According to this further embodiment, with the insert 15 mounted on the drilling body 10, the radially outer portion 26c of the cutting edge 26 is curved, in particular concave, so as to project forward from the remainder (and most of) the length of the cutting edge 26 at a region central and radially inward of the insert 15 with respect to the direction of rotation R. The cutting edge 26 at the radially outer portion 26c may be considered raised to deflect upwardly when viewed end-to-end from the clearance surface 24, thereby increasing the height (and thickness) of the insert 15 within the zone Z2. In particular, the radially outer end 26b of the cutting edge 26 is raised at a height h above a mid-length region of the cutting edge 26 and a region within the radially inner zone Z1. According to this particular embodiment, the cutting edge 26 is curved in the height or thickness direction of the insert 15 (when viewed end-to-end from the clearance face 24) to provide a large radius curved transition portion within the zone Z2, and which extends between about the mid-length position and the radially outer end 26b of the cutting edge 26 (with the outer end 26b being positioned immediately radially inward of the outermost end 35 of the insert 15). According to this particular embodiment, h is greater than the height of the chamfer 29 extending above the major length of the cutting edge 26 corresponding to the chamfer second edge 29 b. Furthermore, h is less than the elevated height of the support surface 23 relative to the majority of the length of the cutting edge 26 (when viewing the insert 15 from the cutting end region (and in particular the clearance surface 24)), as shown in fig. 12 (and 7).

The cutting edge region according to this embodiment is curved, i.e.: is concave in plane P2 (see fig. 3). However, according to further embodiments, the transition may be angled. The radially outer portion 26c of the cutting edge 26 is curved or angled (so as to project forwardly in the direction of rotation R from the remainder of the cutting edge 26), which facilitates the production of tightly curled chips, thus occupying less volume within the formed hole relative to an elongated chip strip or loosely spiraled chips. It will be appreciated that this facilitates the evacuation of chips from the bore and thus improves cutting efficiency and extends the life of the insert and cutting tool.

Claims

1. A metal cutting drilling insert (15) for a drilling tool, the metal cutting drilling insert comprising:

at least one cutting edge (26) formed at an intersection of an adjoining rake surface (25) and a clearance surface (24), the cutting edge (26) having a length that is radially aligned at the tool;

a chip breaker (28) formed as an elevated protrusion or recess at the rake surface (25) and extending from the cutting edge (26);

the method is characterized in that:

comprises a chamfer (29) at the intersection of the rake face (25) and the clearance face (24), the chamfer (29) being positioned at the chip breaker (28), the chamfer (29) being defined relative to the profile of the cutting edge (26) at one or either side of the chip breaker (28), and

wherein the length (B) of the chip breaker (28) in the longitudinal direction along the rake surface (25) is smaller than the remaining length part of the cutting edge (26) between the first and second lateral side (27a, 27B) of the drill insert (15) at one or both sides of the chip breaker (28).

2. The drilling blade of claim 1, configured to cooperate with a second blade (16), the drilling blade (15) and second blade (16) being mountable on the drilling tool at different radial positions such that during rotation of the drilling tool, the drilling blade (15) and second blade (16) radially overlap to define an annular intersection zone (Z1);

wherein the chip breaker (28) is positioned relative to the cutting edge (26) within the intersection zone (Z1).

3. The drill insert according to claim 1 or 2, wherein the chamfer (29) at the chip breaker (28) defines an intersecting surface (18) aligned transversely to the adjoining rake face (25) and clearance face (24), the cutting edge (26) at one or either side of the chip breaker (28) being free of intersecting surfaces and having i) a line shape and/or ii) a width extending between the rake face (25) and the clearance face (24), the line shape and/or the width corresponding to the line shape and/or the width of the intersecting surface (18) at the chip breaker.

4. A drilling insert according to any of the preceding claims 1-2, wherein the length (B) of the chip breaker (28) is 5-60% of the total length (L) of the cutting edge (26), wherein the total length (L) comprises the chamfer (29) and the cutting edge (26) at one or both sides of the chip breaker (28).

5. A drill insert according to any of the preceding claims 1-2, comprising a single chip breaker (28) at the rake surface (25).

6. A drill insert according to any of the preceding claims 1-2, wherein the chamfer (29) at the chip breaker (28) comprises an intersecting surface (18), and the intersecting surface (18) is aligned in a plane perpendicular to the length of the cutting edge (26) in the range of 20 ° to 70 ° with respect to the clearance face (24).

7. A drill insert according to any of the preceding claims 1-2, wherein the chip breaker (28) extends perpendicular to the length of the cutting edge (26), partly or completely in a transverse direction across the rake surface (25).

8. A drilling blade according to claim 2, wherein the drilling blade (15) is a peripheral blade (15) and the second blade is a central blade (16) of the drilling tool, the peripheral blade (15) being intended to cooperate with the central blade (16) of the drilling tool, the peripheral blade (15) and the central blade (16) being positionally defined relative to each other in a radial direction of the drilling tool.

9. An insert according to any of the preceding claims 1-2, comprising a generally rectangular cuboid shape in which the cutting edge (26) extends transversely across the drilling insert (15) at one edge or two opposite edges of the drilling insert (15).

10. A drilling insert according to any one of the preceding claims 1-2, wherein the chip breaker (28) is located on the drilling insert (15) in the longitudinal direction of the cutting edge (26) closer to the first lateral side (27a) of the drilling insert (15) than to the second lateral side (27b) of the drilling insert (15).

11. A drill insert according to claim 10, wherein the chip breaker (28) is positioned in the longitudinal direction of the cutting edge (26) only in the first half of the drill insert closer to the first lateral side (27 a).

12. A drill insert according to any of the preceding claims 1-2, wherein, in the longitudinal direction of the cutting edge (26), a portion (26c) of the cutting edge (26) is curved or angled such that a second end (26b) of the cutting edge (26) closest to a second lateral side (27b) of the drill insert (15) is elevated in relation to a first end (26a) of the cutting edge (26) closest to a first lateral side (27a) of the drill insert (15).

13. A drilling insert according to claim 12, wherein a portion (26c) of the cutting edge (26) closest to the second lateral side surface (27b) is concave to curve upwardly towards the second end (26b) of the cutting edge (26) when the drilling insert (15) is viewed end-to-end from the clearance surface (24).

14. The drill insert according to claim 6, wherein the intersecting surface (18) is aligned in the range of 25 ° to 65 ° relative to the clearance face (24).

15. The drill insert as claimed in claim 6, wherein the intersecting surfaces (18) are aligned in the range of 30 ° to 60 ° relative to the clearance face (24).

16. The drill insert according to claim 6, wherein the intersecting surfaces (18) are aligned in a range of 35 ° to 55 ° relative to the clearance face (24).

17. The drill insert as claimed in claim 6, wherein the intersecting surfaces (18) are aligned in the range of 40 ° to 50 ° relative to the clearance face (24).

18. A metal cutting drilling tool comprising:

an elongated drilling body having an axially forward drilling shaft (11) and an axially rearward shank (12); and

a boring blade (15) according to any of claims 1-17, the boring blade (15) being mountable at an axially forward cutting end (13) of the shaft (11).

19. The drilling tool as claimed in claim 18, wherein the drilling insert (15) is mounted at a radially peripheral region of the drilling tool to form a peripheral insert (15).

20. A drilling tool according to claim 19, further comprising a second insert (16) mounted at or towards a radially central region of the drilling tool to form a central insert (16) with respect to the peripheral insert (15).

21. A drilling tool according to claim 20, comprising a single peripheral blade (15) and a single central blade (16) mounted at the axially forward cutting end (13) of the shaft (11).

22. The drilling tool according to claim 20 or 21, wherein the peripheral blade (15) and the central blade (16) are mounted on the drilling tool such that during rotation of the drilling tool the peripheral blade (15) and the central blade (16) radially overlap to define an annular intersection zone (Z1);

23. The drilling tool as claimed in claim 22, wherein a majority of the chip breaker (28) is located within the intersection zone (Z1) in a radial direction.

24. A drilling tool according to any of claims 18-19, wherein the shaft (11) comprises chip flutes (17), the chip flutes (17) extending axially rearwardly from the axially forward cutting end (13) towards the shank (12).